The present invention generally relates to a head carriage device, and more particularly to a head carriage device for use in a disk recording/reproducing unit, which provides greater flexibility to the design of a thin-type, small-sized disk recording/reproducing unit.
In a disk recording/reproducing unit which uses a flexible disk as a recording medium, a magnetic head mounted on a head carriage device is arranged such that the magnetic head is slidably movable in a radial direction of the flexible disk and positionable to read or write data on the flexible disk. An example of a dual side recording type head carriage device is shown in FIGS.8 and 9. This head carriage device 10 is mounted within a disk recording/reproducing unit which uses as the recording medium a 3.5-inch flexible disk accommodated in a disk case with head access windows formed therein. The head carriage device 10 generally has a carriage member 11 and an arm 12 and can be moved relative to the disk recording/reproducing unit by means of a drive means (not shown) in a direction as indicated by an arrow A.sub.1 -A.sub.2 in FIG. 8. The head drive part may be, for example, a steel belt connected to a drive motor provided in the disk drive unit.
The arm 12 is connected to the carriage member 11 by a flexible member 12a, this flexible member 12a resiliently biasing the arm 12 so that the arm is movable or rotatable in a direction as indicated by an arrow B.sub.1 -B.sub.2 in FIG. 8. An upper magnetic head 13 is mounted on bottom of the arm 12 and a lower magnetic head 14 is mounted on top of the carriage member 11. These magnetic heads 13, 14 are arranged at end portions of the arm 12 and the carriage member 11 in the direction A.sub.1 such that the two heads 13, 14 are opposed to each other when a disk case 15 in which a flexible disk 16 is accommodated is inserted into the disk recording/reproducing unit. The disk case 15 has disk access windows 15a formed in top and bottom surfaces of the disk case 15, respectively. The magnetic heads 13, 14 during operation are placed onto the flexible disk 16 through the disk access windows 15a so that the magnetic heads 13, 14 slidably contact the top and bottom surfaces of the flexible disk 16 to read or write data.
Conventionally, the magnetic heads 13, 14 which are opposed to each other in the head carriage device 10 are formed with the same size and shape, and a height of the magnetic head 13 from a top surface of the flexible disk 16 to the arm 12, as indicated by a letter H in FIG. 8, which is also called a slider height, is substantially equal to a height of the magnetic head 14 from the carrier member 11 to a bottom surface of the disk 16, as indicated by a letter H in FIG. 8. In recent years, there is the demand for small-sized personal computers in which a disk recording/reproducing unit is installed, and a thin-type, small-sized disk recording/reproducing unit is desired by manufacturers for the use in personal computers.
In the conventional head carriage device 10, the magnetic heads 13, 14 are formed with the same height, and therefore a predetermined height of each of the magnetic heads 13, 14 is required for making the magnetic heads positionable to read or write data on the flexible disk 16 accommodated in the disk case 15. For example, the disk case 15 for use in the conventional head carriage device 10 is 3.3+/-0.2 mm thick, and therefore the minimum heights of the magnetic heads 13, 14 in total must be greater than 3.5 mm. Moreover, a clearance in vertical direction between the carriage member 11 and the disk case 15 and a clearance in vertical direction between the arm 12 and the disk case 15 are needed, and therefore the actual height of each of the magnetic heads 13, 14 used for the head carriage device is usually between 2.5 mm and 2.7 mm.
On the other hand, in the head carriage device, the arm 12 is arranged such that it is movable or rotatable relative to the carriage member 11 in a direction as indicated by an arrow B.sub.1 in FIG. 8 by means of a suitable moving mechanism (not shown). When the disk case 15 is inserted into or demounted from the disk recording/reproducing unit, the arm 12 must be moved upwardly for preventing the magnetic heads 13, 14 from interfering with the disk case 15. In a case where the magnetic heads 13, 14 have a predetermined height, it is necessary to move the arm 12 upwardly from the carriage member 11 so that the magnetic heads 13, 14 are safely released from the positions thereof where the magnetic heads 13, 14 slidably contact the flexible disk 16 through the disk access windows 15a of the disk case 15. Accordingly, there is a problem in that the disk recording/reproducing unit in which the above mentioned head carriage device requiring such an arm movement space at an upper location is provided has an unnecessarily great height and becomes bulky, the arm movement space allowing the arm 12 to move upwardly as described above.
Moreover, because the magnetic heads 13, 14 in the conventional head carriage device have the same height from the flexible disk 16, the location of the head carriage device 10 to be arranged in the disk recording/reproducing unit is restricted. A feasible design of the disk recording/reproducing unit which is located in the vicinity of the head carriage device is limited, and there is no flexibility in selecting the design owing to the specified height of the magnetic heads.